CN104518788A - System and method for a voltage controlled oscillator - Google Patents

Abstract

According to an embodiment, a voltage controlled oscillator (VCO) includes: a VCO core having a plurality of transistors; a bias resistor coupled between a collector terminal of the VCO core and a first supply node; and an emitter terminal coupled to the VCO core Sub-Varactor circuit. The bias resistors are configured to limit the self-bias conditions of the VCO core.

Description

Systems and methods for voltage controlled oscillators

technical field

The present disclosure relates generally to electronic devices, and more particularly to systems and methods for voltage controlled oscillators (VCOs).

Background technique

Applications in the mmWave frequency region have gained significant interest over the past few years due to the rapid development of low-cost semiconductor technologies such as silicon germanium (SiGe) and good geometry complementary metal-oxide-semiconductor (CMOS) processing. The availability of high speed bipolar transistors and metal oxide semiconductor (MOS) transistors has created a growing demand for integrated circuits for 60GHz, 77GHz and 80GHz and beyond 100GHz millimeter wave applications. Such applications include, for example, automotive radar and multi-gigabit communication systems.

In some radar systems, the range between the radar and the target is determined by transmitting a frequency modulated signal, receiving reflections of the frequency modulated signal, and determining the distance based on the time delay and/or frequency difference between transmission and reception of the frequency modulated signal Determine the distance. The resolution, accuracy, and sensitivity of a radar system may depend in part on the phase noise performance and frequency agility of the radar's frequency generation circuitry, which typically includes an RF oscillator and circuitry to control the frequency of the RF oscillator.

However, as the operating frequency of RF systems continues to increase, the generation of such high frequency signals poses a major challenge. Oscillators operating at high frequencies may suffer from poor phase noise performance resulting from 1/f and termination noise in devices including VCOs. Phase noise can also be compromised by nonlinear effects of self-biasing conditions that affect the gain and tuning characteristics of the VCO.

Contents of the invention

According to an embodiment, a voltage controlled oscillator (VCO) includes: a VCO core having a plurality of transistors; a bias resistor coupled between a collector terminal of the VCO core and a first supply node; and an emitter terminal coupled to the VCO core Sub-Varactor circuit. The bias resistors are configured to limit the self-bias conditions of the VCO core.

Description of drawings

For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

Figures 1a-1d illustrate the operation of an example automotive radar system, a diagram of a conventional VCO, and the performance of a conventional VCO;

Figures 2a-2b illustrate a diagram of an embodiment VCO;

Figures 3a to 3f illustrate the execution results of the embodiment VCO;

Figure 4 illustrates a block diagram of an embodiment method; and

Figure 5 illustrates an embodiment radar system.

Corresponding reference numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The drawings are drawn to clearly illustrate the relevant aspects of the preferred embodiments and are not necessarily drawn to scale. To more clearly illustrate certain embodiments, text indicating variations of the same structure, material, or processing step may follow a figure number.

Detailed ways

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

The invention will be described with respect to preferred embodiments in a specific context, system and method for a radar system, such as an automotive radar system. The invention can also be applied to other systems and applications using RF oscillators, such as general radar systems and wireless communication systems.

In an embodiment of the invention, a low phase noise VCO utilizes a feedback resistor to limit the effect of the self-bias during operation. This limitation on the self-bias voltage also mitigates distortion of the varactor tuning characteristics produced by modulation of the varactor during operation of the VCO, thereby preventing possible increases in phase noise or reduction in frequency generating systems such as phase-locked loops (PLLs). Undesired VCO gain variation for small lock range of the same PLL. In addition, phase noise suppression can be achieved by decoupling the harmonics of the VCO core from the varactor.

FIG. 1 a illustrates an example automotive radar scenario 100 in which a car has an automotive radar system 104 . The automotive radar system 104 transmits and receives, for example, frequency modulated continuous wave (FMCW) signals, and detects reflections of this transmitted signal in order to determine the distance between the automotive radar system 104 and other vehicles or objects on the road. In the illustrated scenario, a large vehicle 106 such as a truck is closer to the car 102 than a small vehicle 108 such as a motorcycle. Under normal operating conditions, the echo or reflection of the large vehicle 106 may have a higher magnitude compared to the reflection of the small vehicle 108 because the large vehicle 106 is larger and closer than the small vehicle 108 .

Figure 1 b illustrates a graph 120 of received signal level versus received frequency for the scenario of Figure 1 a. Signal level versus frequency curve 122 corresponds to received reflections from large vehicle 106 , and frequency f1 of signal level peak 130 corresponds to the distance between automotive radar system 104 and large vehicle 106 . Similarly, signal level versus frequency curve 126 corresponds to received reflections from small vehicle 108 , and frequency F2 of signal level peak 132 corresponds to the distance between automotive radar system 104 and small vehicle 108 . Thus, the distance between the large vehicle 106 and the small vehicle 108 is proportional to the separation between the frequencies F1 and F2.

Along with the desired output signal, the phase noise of the radar transmitter is also transmitted and reflected. Phase noise reflected from large vehicle 106 is represented as dashed line 124 . As can be seen in graph 120 , phase noise 124 affects the radar's ability to receive signals reflected from small vehicle 108 . The signal-to-noise ratio between signal level peaks 132 due to small vehicles 108 and corresponding noise floors due to phase noise reflected from large vehicles 106 is represented as length 134 . As can be seen from the graph of FIG. 1B , phase noise affects the ability of the automotive radar system 104 to discern small and distant objects. The greater the phase noise of the radar transmitter, the less capable the radar system is of distinguishing small and distant objects.

Figure 1c illustrates a conventional VCO 150 according to a "push-push" architecture. The VCO includes a VCO core 151 having a transistor 153 and an inductor 154 , a matching network 152 , a varactor 158 and a current source 160 . The transistor 153 is biased according to the bias voltage V _bias , and the capacitance of the varactor 158 is tuned according to the tuning voltage V _tune . The oscillation frequency of the VCO150 is approximately:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; OSC</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 154</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 158</span>}}}}<span\; class="notranslate">\; ,</span>$

Wherein, L ₁₅₄ is the inductance of the inductor 154 , and C ₁₅₈ is the capacitance of the varactor 158 . The output of VCO 150, denoted _Vout , provides an output frequency that is twice _fOCS .

Varactor 158 may be implemented as a diode capacitance that is inversely proportional to the voltage across its terminals. This decrease in applied voltage is likely due to an increase in the width of the depletion region in the reverse biased diode producing a corresponding decrease in its capacitance value. An example relationship of the capacitance value C _varactor of the DC varactor with respect to the tuning voltage is shown as curve 170 in FIG. 1d. As shown, the C _varactor decreases with increasing voltage. However, during operation of the VCO, the actual voltage across varactor 158 varies over time during each oscillation cycle of the VCO, thereby causing the capacitance value to vary during each oscillation cycle of the VCO. Curves 174, 176a, 176b, and 176c represent changes in the tuning voltage applied across varactor 158 due to a change in the output of the VCO over a cycle. Curves 176a-176c represent small VCO amplitudes and curve 174 represents large VCO amplitudes. As shown, when the VCO produces a large amplitude represented by curve 174, the capacitance value of varactor 158 changes from a capacitance value C1 corresponding to point 173 on curve 170 to a capacitance corresponding to point 175 on curve 170. Value C2. The net net effect in this large signal behavior is to produce a change in the effective tuning characteristic of varactor 158 . These effective tuning characteristics are denoted C _eff in Fig. 1c. Curve 178 represents the effective tuning characteristic corresponding to the small amplitude curves 176 a to 176 c , and curve 180 represents the effective tuning characteristic corresponding to the large amplitude curve 174 . As shown, the curve 180 representing C _eff for large signal amplitudes has a "knee" in its tuning characteristic. This "knee" can result in reduced VCO gain, which can affect the PLL's ability to achieve frequency lock within the VCO tuning range, and can increase phase noise when the VCO is operating in the high K _VCO tuning range.

Figure 2a illustrates a VCO 200 comprising a VCO core 202, a varactor circuit 204 including a varactor 230, and a bias circuit 210 according to an embodiment of the present invention. In an embodiment, the VCO core includes transistor 212 , capacitor 214 and transmission line element 216 . In an embodiment, the VCO is configured to oscillate at a frequency between about 5 GHz and about 40 GHz, for example about 20 GHz. However, in alternative embodiments, other oscillation frequency ranges may be used. Transmission line element 216 may be sized to create an inductive impedance at the base of transistor 212 . The bias voltage to the base of transistor 212 is provided by bias circuit 210 coupled to VCC via transmission line element 222 . In an embodiment, transmission line element 222 is sized to have a quarter wavelength at twice the oscillation frequency of VCO 200 . In some embodiments, bias voltage V _BIAS is filtered via bias filter network 207 having transmission line element 240 and capacitor 242 . In some embodiments, transmission line element 240 has a quarter wavelength at approximately four times the oscillation frequency of VCO 200 .

The collector of transistor 212 is coupled to VCC via transmission line element 218 , feedback resistor 220 and transmission line element 222 . In an embodiment, transmission line element 218 is sized to maximize signal swing. Feedback resistor 220 in some embodiments mitigates the self-biasing effect of high VCO amplitudes that distorts the curve of varactor 230 . For example, at low temperatures and/or fast process angles, the tendency of transistor 212 to increase gain and current in the VCO and varactor nodes producing larger signal swings is controlled by the action of feedback resistor 220 offset. An increase in the bias current and/or signal swing that produces an increased current produces a voltage drop across the feedback resistor 220 . This voltage drop suppresses the signal swing of the VCO core 202 and thus reduces the effect of self-biasing effects on the tuning characteristics of the VCO. On the other hand, at high temperatures and/or slow process angles, the tendency of transistor 212 to decrease in gain and current limits the occurrence of self-biasing such that the additional voltage drop across feedback resistor 220 is negligible and/or not produce a suitable reduction in VCO amplitude. In some embodiments, the feedback resistor has a resistance value between about 5Ω and about 10Ω for a bias current of about 20mA. Alternatively, bias current and other resistance values for feedback resistor 220 may be used.

Varactor circuit 204 includes varactor element 230 , AC coupling capacitor 228 , series transmission line element 232 , and an RF choke circuit including transmission line elements 234 and 236 and capacitor 238 . In some embodiments, tuning voltage V _TUNE is filtered via bias filter network 208 having transmission line element 244 and capacitor 246 . In some embodiments, transmission line element 240 has a quarter wavelength at approximately four times the oscillation frequency of VCO 200 . The combination of each RF choke circuit and transmission line element 232 may form an inductive voltage divider. In an embodiment, AC coupling capacitor 228 enables biasing of varactor 230 based on applied tuning voltage V _TUNE and reference voltage V _n1 . Series transmission line element 232 and AC coupling capacitor 228 form a series resonant circuit that passes the fundamental frequency of the oscillator to the varactor while attenuating the harmonics of VCO 200 . In some embodiments, the series transmission line element 232 may be implemented using a transmission line having a length of approximately 400 μ in one example. In another example, the length of the series transmission line element 232 may be between about 100 μ to about 500 μ. However, it should be understood that the length of the series transmission line element 232 may be outside this range depending on the embodiment and its specification. In some alternative embodiments, inductive elements may be used to implement series transmission line element 232 .

In an embodiment, the RF choke circuit comprising transmission line elements 234, 236 and capacitor 238 produces a high impedance to the emitter of transistor 212 at approximately twice the oscillation frequency of VCO 200 and provides lower impedance at other harmonics of the oscillation frequency. of impedance. By providing a lower impedance to oscillation harmonics via the series transmission line element 232 and the RF choke circuit, phase noise may be improved due to the reduced nonlinear behavior of the varactor.

The output V _OUT of VCO 200 is coupled to the emitter of transistor 212 via transmission line elements 224 and 226 isolating the VCO core from the output, thereby forcing the VCO's fundamental frequency signal to remain in the VCO core. This also improves the quality factor of the varactor and results in better phase noise performance. Tail current for transistor 212 is provided by transmission line element 248 and resistor 250 . In an embodiment, transmission line element 248 has a quarter wavelength at approximately twice the resonant frequency of VCO 200 .

It should be understood that in some embodiments, the dimensions of the transmission elements within VCO 200 may vary from the aforementioned lengths and their corresponding wavelengths depending on the particular embodiment and its details.

Figure 2b illustrates a VCO 260 according to yet another embodiment of the present invention. VCO 260 is similar to VCO 200 shown in Figure 2a, except with the addition of output filter 274 and various alternative implementation details. In an embodiment, transmission line element 222 is divided into series transmission line elements 222a and 222b, transmission line element 248 is divided into series transmission line elements 248a and 248b, and transmission line element 216 is divided into transmission line elements 216a and 216b. Similarly, the emitter of transistor 212 is coupled to common node N2 via transmission line elements 226a through 226d. In varactor circuit 204 , transmission line element 236 is coupled to ground via resistor 262 and capacitor 264 .

In an embodiment, bias circuit 210 provides bias voltage V _BIAS via transmission line elements 292 a - 292 b , resistor 296 , diode-coupled transistors 298 a - 298 c , and capacitor 291 . The emitters of transistors 298 a - 298 c are coupled to ground via resistor 299 . Output filter 274 is coupled between node N2 and output port V _OUT . In an embodiment, filter 274 is a bandpass filter centered at approximately twice the oscillation frequency of VCO 260 . Alternatively, other filter types and center frequencies may be used. Filter 274 is implemented as an LC ladder circuit having capacitors 276 , 280 , 284 , 286 and 290 and an inductor implemented using transmission line elements 278 , 282 and 288 . In yet another alternative embodiment, the inductor may be implemented using discrete or on-chip inductors.

Figure 3a illustrates a series of curves representing equivalent capacitance values over frequency for various embodiment architectures. Curve 302 represents the performance of a VCO with feedback resistor 220 without series transmission line element 232 and without the RF choke formed by transmission line elements 234, 236 and capacitor 238; , 236, and capacitor 238 without the VCO performance of the VCO with the series transmission line element 232; 232 VCO performance. As can be seen, curve 306 has higher effective capacitance values at higher frequencies and lower effective capacitance values at lower frequencies, thereby increasing the tuning range of the VCO.

Fig. 3b illustrates a spectrogram of a measurement of the output V _OUT of the VCO 200 shown in Fig. 2a. Here, the output frequency of the VCO 200 is about 40 GHz, which is twice the oscillation frequency of the VCO, 20 GHz. FIG. 3 c illustrates a phase noise graph showing the phase noise performance of VCO 200 . As shown, the phase noise is about -82.76dBc/Hz at an offset of 50KHz, about -90.66dBc/Hz at an offset of 100KHz, about -110.48dBc/Hz at an offset of 1MHz, and at An offset of 10MHz is approximately -129.12dBc/Hz.

Figure 3d illustrates a graph of oscillation frequency versus tuning voltage for an embodiment VCO. Trace 310 shows the relationship between oscillation frequency and tuning voltage at 25°C, and trace 312 shows the relationship between oscillation frequency and tuning voltage at 130°C. Figure 3e illustrates a graph of VCO gain (KVCO) versus tuning voltage for the embodiment VCO characterized in Figure 3d. Trace 316 shows the VCO gain versus tuning voltage at 25°C, and trace 314 shows the oscillation frequency versus tuning voltage at 130°C. Fig. 3f illustrates the relationship between the oscillation frequency and the supply voltage VCC at various tuning voltages at 25°C. Trace 320 shows the oscillation frequency versus a tuning voltage of about 0V, trace 322 shows the oscillation frequency versus a tuning voltage of about 2.5V, and trace 324 shows the oscillation frequency versus a tuning voltage of about 5.0V. It should be appreciated that the graphs of Figures 3a-3f illustrate the performance of example embodiments. Other embodiment VCOs may perform different behaviors than those illustrated in Figures 3a-3f.

FIG. 4 illustrates a block diagram 400 of an embodiment method of operating a VCO. At step 402, a supply voltage is applied to the VCO core via a resistor. In an embodiment, the VCO core and feedback resistor may be implemented using a circuit similar to VCO core 202 and feedback resistor 220 shown in FIG. 2a. At step 404, this resistor can be used to limit self-bias conditions. In some embodiments, limiting self-bias conditions can mitigate the effect of self-bias on the effective capacitance value of the VCO. In step 406, the VCO is tuned by applying a tuning voltage to the varactor, and in step 408, a signal path is provided between the VCO core and the varactor at the oscillation frequency. In some embodiments, this signal path uses a series resonant circuit with an AC coupling capacitor and a transmission line element such as shown in FIG. accomplish. At step 410, the harmonics of the VCO are shunted to a reference node such as ground using, for example, an RF choke circuit. In some embodiments, by performing steps 408 and 410, the harmonics of the VCO coupled to the varactor are attenuated, thereby improving the phase noise performance.

FIG. 5 illustrates a single-chip radar transmission system 500 including an upconverter 502 , a power amplifier 504 and a frequency generation circuit 506 . As shown, the upconverter 502 upconverts the baseband signal BB to a higher frequency signal, which is then amplified by the power amplifier 504 and output on pin OUT. In some embodiments, the baseband signal BB may be a frequency sweep or other signal type used in radar systems. The frequency generation circuit 506 generates a local oscillator signal LO based on a reference frequency at pin REF, which can be generated using, for example, a crystal oscillator. In an embodiment, frequency generation circuit 506 may be implemented using a phase locked loop (PLL) with phase detector 512 , loop filter 510 , VCO 508 and voltage divider 514 . VCO 508 may be implemented using the embodiment VCOs described herein. It should be appreciated that system 500 is but one example of many examples of embodiment systems in which embodiment oscillators may be used. Alternative systems may include, for example, wireless and wired communication systems and other systems that use VCOs.

According to an embodiment, a voltage controlled oscillator (VCO) includes a VCO core having a plurality of transistors, a bias resistor coupled between a collector terminal of the VCO core and a first supply node, and an emitter terminal coupled to the VCO core the variable capacitance circuit. The bias resistors are configured to limit the self-bias conditions of the VCO core.

In an embodiment, the varactor circuit includes a first capacitor having a first terminal coupled to the emitter node of the VCO core, a first transmission line element having a first terminal coupled to a second terminal of the first capacitor, a first transmission line element having a first terminal coupled to the The first terminal of the second terminal of the first transmission line and the first varactor diode coupled to the second terminal of the tuning node, the RF choke circuit coupled between the second terminal of the first capacitor and the second reference node. The first transmission line may comprise a length of at least 100 μm, and the RF choke circuit may have a quarter wavelength at approximately twice the operating frequency of the VCO. In some embodiments, the first transmission line and the RF choke form an inductive voltage divider.

In an embodiment, the VCO further includes a fourth transmission line element coupled between the tuning node and the input tuning terminal, a third capacitor coupled between the input tuning terminal and the second reference node, a base bias voltage coupled at the VCO core A fifth transmission line element between the node and the output node of the bias circuit, and a fourth capacitor coupled between the output node of the bias circuit and the second reference node. The fourth transmission line element may have a quarter wavelength at approximately four times the operating frequency of the VCO, and the fifth transmission line element may have a quarter wavelength at approximately four times the operating frequency of the VCO.

In an embodiment, the RF choke circuit includes a second transmission line element having a first terminal coupled to a first terminal of the first transmission line element, a third transmission line having a first node coupled to a second terminal of the second transmission line element element, and a second capacitor coupled between the first node of the first transmission line and the second reference node. The VCO may include an output node coupled to the emitter terminal of the VCO core. In an embodiment, the VCO includes an operating frequency between about 10 GHz and about 30 GHz.

According to yet another embodiment, a voltage controlled oscillator (VCO) includes a VCO core having a plurality of transistors, and a varactor circuit coupled to an emitter terminal of the VCO core. The varactor circuit includes a first capacitor having a first terminal coupled to an emitter node of the VCO core, a first transmission line element having a first terminal coupled to a second terminal of the first capacitor, a first transmission line element having a first terminal coupled to the first transmission line element The first terminal of the second terminal and the first varactor coupled to the second terminal of the tuning node, and the RF choke circuit coupled between the second terminal of the first capacitor and the second reference node.

In an embodiment, the RF choke circuit includes a second transmission line element having a first terminal coupled to a first terminal of the first transmission line element, a third transmission line having a first node coupled to a second terminal of the second transmission line element element, and a second capacitor coupled between the first node of the first transmission line and the second reference node. The first transmission line may have a length of at least 100 μm, the first transmission line element and the RF choke may form an inductive voltage divider. In some embodiments, the RF choke circuit has a quarter wavelength at approximately twice the operating frequency of the VCO.

In an embodiment, the VCO further includes a resistor coupled between a common supply node of the VCO core and a power input terminal of the VCO. This resistor can have a resistance value between about 1 ohm and about 20 ohms. Alternatively, other values may be used. In some embodiments, the VCO further includes a fourth transmission line element coupled between the power supply input terminal and the aforementioned resistor such that the fourth transmission line element has a quarter wavelength at approximately twice the operating frequency of the VCO.

According to yet another embodiment, a method of operating a voltage controlled oscillator (VCO) includes: applying a supply voltage to the VCO core via a resistor coupled to a collector terminal of the VCO core; limiting a self-bias condition of the VCO core via the resistor; and Tuning the VCO includes applying a tuning voltage to a varactor coupled to an emitter terminal of the VCO core.

The method may also include: providing a signal path at the oscillation frequency of the VCO between the tuning node and the emitter terminal of the VCO core using a first transmission line element; and via an RF choke coupled between the emitter terminal of the VCO core and the reference node A current circuit to couple the harmonics of the VCO to the reference node. In some embodiments, the RF choke has a quarter wavelength at approximately twice the oscillation frequency of the VCO.

The method may also include filtering the tuning node using a second transmission line element coupled between the tuning terminal of the VCO and the tuning node. The second transmission line element may have a quarter wavelength at approximately four times the oscillation frequency of the VCO.

Advantages of embodiments of the present invention include the ability to generate frequencies with very low phase noise. Another advantage includes, for example, a wide VCO tuning range.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description.

Claims (22)

1. a voltage controlled oscillator (VCO), comprising:

VCO core, described VCO core comprises multiple transistor;

Bias resistor, between the collector terminal that described bias resistor is coupling in described VCO core and the first supply node, wherein said bias resistor is configured to the autobias condition limiting described VCO core; And

Transfiguration circuit, described transfiguration which couple is to the emitter terminal of described VCO core.

2. VCO according to claim 1, wherein said transfiguration circuit comprises:

First capacitor, described first capacitor has the first terminal of the emitter node being coupled to described VCO core;

First transmission line element, described first transmission line element has the first terminal of the second terminal being coupled to described first capacitor;

First variable capacitance diode, described first variable capacitance diode has the first terminal of the second terminal being coupled to described first transmission line and is coupled to the second terminal of tuning node; And

RF choke circuit, between the second terminal that described RF choke circuit is coupling in described first capacitor and the second reference node.

3. VCO according to claim 2, wherein:

Described first transmission line comprises the length of at least 100 μm; And

Described RF choke circuit has quarter-wave at about twice place of the frequency of operation of described VCO.

4. VCO according to claim 2, wherein said first transmission line and described RF chokes form inductive voltage divider.

5. VCO according to claim 2, also comprises:

4th transmission line element, described 4th transmission line element is coupling in described tuning node and inputs between tuning terminal;

3rd capacitor, described 3rd capacitor-coupled is between the tuning terminal of described input and described second reference node;

5th transmission line element, between the base bias node that described 5th transmission line element is coupling in described VCO core and the output node of bias circuit; And

4th capacitor, described 4th capacitor-coupled is between the described output node and described second reference node of described bias circuit.

6. VCO according to claim 5, wherein:

Described 4th transmission line element has quarter-wave at about four times of places of the frequency of operation of described VCO; And

Described 5th transmission line element has quarter-wave at about four times of places of the described frequency of operation of described VCO.

7. VCO according to claim 2, wherein said RF choke circuit comprises:

Second transmission line element, described second transmission line element has the first terminal of the described the first terminal being coupled to described first transmission line element;

3rd transmission line element, described 3rd transmission line element has the first node of the second terminal being coupled to described second transmission line element; And

Second capacitor, described second capacitor-coupled is between the first node and described second reference node of described first transmission line.

8. VCO according to claim 1, wherein said VCO comprise the output node of the described emitter terminal being coupled to described VCO core.

9. VCO according to claim 1, wherein said VCO are included in the frequency of operation between about 10GHz to about 30GHz.

10. a voltage controlled oscillator (VCO), comprising:

VCO core, described VCO core comprises multiple transistor; And

Transfiguration circuit, described transfiguration which couple is to the emitter terminal of described VCO core, and wherein said transfiguration circuit comprises:

First capacitor, described first capacitor has the first terminal of the emitter node being coupled to described VCO core,

First transmission line element, described first transmission line element has the first terminal of the second terminal being coupled to described first capacitor,

First variable capacitance diode, described first variable capacitance diode has the first terminal of the second terminal being coupled to described first transmission line and is coupled to the second terminal of tuning node, and

RF choke circuit, between the second terminal that described RF choke circuit is coupling in described first capacitor and the second reference node.

11. VCO according to claim 10, wherein said RF choke circuit comprises:

Second transmission line element, described second transmission line element has the first terminal of the described the first terminal being coupled to described first transmission line element,

3rd transmission line element, described 3rd transmission line element has the first node of the second terminal being coupled to described second transmission line element, and

Second capacitor, described second capacitor-coupled is between the first node and the second reference node of described first transmission line.

12. VCO according to claim 10, wherein said first transmission line comprises the length of at least 100 μm.

13. VCO according to claim 10, wherein said first transmission line element and described RF chokes form inductive voltage divider.

14. VCO according to claim 10, wherein said RF choke circuit has quarter-wave at about twice place of the frequency of operation of described VCO.

15. VCO according to claim 10, also comprise the resistor between public supply node and the power input terminal of described VCO being coupling in described VCO core.

16. VCO according to claim 15, wherein said resistor has the resistance value between about 1 ohm to about 20 ohm.

17. VCO according to claim 15, also comprise the 4th transmission line element, described 4th transmission line element is coupling between described power input terminal and described resistor, and wherein said 4th transmission line element has quarter-wave at about twice place of the frequency of operation of described VCO.

The method of 18. 1 kinds of operation voltage controlled oscillators (VCO), described method comprises:

Resistor via the collector terminal being coupled to VCO core applies supply power voltage to described VCO core; And

The autobias condition of described VCO core is limited via described resistor; And

Tuning described VCO, the transfiguration circuit comprised to the emitter terminal being coupled to described VCO core applies tuning voltage.

19. methods according to claim 18, also comprise:

Use the first transmission line element between tuning node and the described emitter terminal of described VCO core, be provided in the signal path at the frequency of oscillation place of described VCO; And

Via the RF choke circuit be coupling between the described emitter terminal of described VCO core and reference node by the Harmonic coupling of described VCO extremely described reference node.

20. methods according to claim 19, wherein said RF chokes have quarter-wave at about twice place of the frequency of oscillation of described VCO.

21. methods according to claim 19, also comprise: use the second transmission line element be coupling between the tuning terminal of described VCO and described tuning node to come described tuning node filtering.

22. methods according to claim 21, wherein said second transmission line element has quarter-wave at about four times of places of the frequency of oscillation of described VCO.